Electrical well logging method and apparatus



OR 2',712,6:'z CH y 5, 1955 HENRGEORGEs DOLL 2,7l2,632

ELECTRCAL WELL LOGGNG METHOD AND APPARATUS Ori ina1 Fi1ed Nov. 18 1948 3 Sheets-Sheet 1 V AMPLIFIER |NVENTOR HENR|-GEORGES DOLL J y 1955 HENRGEORGES DOLL 2' ELECTRCAL WELL LOGGNG METHOD AND APPARATUS 0ri ina1 Fi1ed Nov. 18. 1948 NVENTOR. HENR|-GEORGES DOLL Jul 5, 1955 HENRGEORGEs DOLL 2,7l2,632

ELECTRICAL WELL LOGGNG METHOD AND APPARATUS ori ina1 F11ed Nov. 18 1948 5 Sheets-Sheet 3 AMPLIFIER INVENTOR HENRGEORGES DOLL as a unit to dieent positions in the bore hole, passing electric current betveen Points near the tvv outer elec trodes of said three and a reference p0int longitudinally Spaced apart therefr0m, adjusting the intensity of the clll rent nowing at said points at each of Said p08itions of the electrodes or required t0 nlaintain Said VO Outer electrodes at a Substantialy constant p0tential With fespect t0 a reference point Substantially at ground potential, and obtaining indications of variations in the average potential dierence between the third electrode Of Said three and each of said tWO Outer electrodes 3. In a nlethod of investigating an electrical property 0f earth formations traversed by a bore hole containing a conducting liquid, tile Steps of disp08ing in the bore hole at least three longitudinally Spaced-apartelectr0des, nving Said electrodes as a unit to different positions in the bore hole, passing Periodically varying current betvveen a reference point longitudina11y Spaced apart fron1 said electrodes and t-0 points 10cated near the tvV0 0uter electrodes, respectively, of Sai(1 three, adjusting the intensity of the current Hovving at said oints at each of said positions of the electrodes aS Tequired to Inaintain Said two outer electrodes at a Substantially constaht periodically varying p0tential Vil respect to a reference point substantially at ground p0tential, and obtaining indications of Variations in periodically varying p0tential difference between t1e third electfode of Said hTee and said tvv0 0uter electrodes,

4. In a nethod 0f investigating an electrical property of earth fornlations Taversed by a bore hole containing a conducting liquid, the Ste )S Of disposing in the bore hole at leaSt three 10ngitudinany Spacedapart electrodes, Inoving said electrodes as a unit to dierent positions in the bore hole, passing peri0dically varying current between a reference point longitudinally spaced apart from Said electr0des and two points 10cated near the tw0 0uter electrodes, respectively, 0f Said three, adj11sting the intensity of the current Owing at Said p0ints at each of Said positions of the electrodes aS Tequired to maintain Said tvo Outer eecr0deS at a Substantially constant periodically vafying Potential vith Tespect to a reference point Substantial1y at ground p0tential, and obtaining in dications of variations in the inten3ity of the current OWing at Said Points In a method Of investigating earth forlnations traversed by a bofe hole containing a relatively conductive liquid, the Steps of lovvering int() the bOle hole at east three 10ngitudinally Spaced-apart electrodes, moving said electrodes as a unit t0 different positions in the bore hole, passing electric c[111ent between a St Point near one of the outer electrodes of Said three and a reference p0int longitudinally Spaced apart therefrom, adjusting The i1- tensity of the current 0Wing at said rSt point at each of Said POSitions of the electrodes aS required to Inaintain said one Outer eIectrode at a Substantialy constant p0 tential with respect to a reference point Substanialy at ground p0tential, passing electric current betvveen a Sec Ond point near he other Of Said outer electrodes of Said three and a reference p0int 10ngitudina11y spaced apart herefrom, adjusting the current fi0wing at sad second oint at each of Said p0sitions of the electr0(]]es aS re quired t0 nlaintain Said other outer electrode at a Sub stantially constant potential with respect t0 a reference point Substantially at ground potential, and obtaining indications of variations in the potential dierence be tvveen the third electrode 0f Said three and at least one of said outer electrodes' 6' In Well logging apparatus, the combination of an electrode array adapted t0 be 10Wered int() a bore hole, Said aTray c0mprising inner and outer pairs of longitudinally Spaced-apart electrodes and an electrode inter- Inediate the electrodes of Said inner paif, a Source of elec trical energy connected to the electrodes of one Of Said pairs and t0 a reference p0int 10ngitudinally Spaced apart therefrom, Said source being responsive to the potentia1 0f tlle electrodes of the other pair with respect to ground for controlling the P0tential of Said other pair of electrodes to Inaintain the same at a reference value vith Tespect to ground, and means for obtaining indicat...0ns of the potential difference betveen said intermediate electrode and Said other pair of electrode3,

7( In apparatus for investigating thte electrical C0nductivity of earth forn1ations traversed by a bore hole containing a Conductive li(11id, an electrode array adapted to be passed through the bore h0le, Said rray C0Inprising inner and outer pairs of longitudinany Spaced apart electrodes and an electrode nterlediate the elec trodes of Said inner pair, Ineans responsive to the potential of said in1er pair of electrodes with respect to ground for passing alternating current from the e]ecfrodes in Said outer pair t0 a reference pcint longitudinally Spaced apart therefr0m fol' aut0matically maintaining Said inner pair of electrodes at Substantially he Same potential vvith respect t() ground, and nleanS for obtaining indications of the potential dieTence betven Said intermediate electrode and said inner pair of elec tfodes 8' In Wel logging apparatus, the combination of an electrode array adapted t0 be 10Wered into a bote hole Said array comprising inner and outer pairs of longi tudinally Spaced-apart electrodes and an electrode intermediate the electrodes of said inner pair, ampnner means having input terminals connected '0 a reference p0int longitudinaly Spaced apart from said electrodes and t0 0ne of Said pairs of electr0des, respectively, and having output termiRals connected to a Teference point substantially at ground potential and to said other pair of elec trodes, respectively, Said amplier means being connected for degenerative feedback between the output and input terminals there0f, a source 0f voltage connected in Series vith Said amplier input terIninals, and neans for obtaining indications of the potentia1 dierence between Said intern1ediate electrode and said one pair of electrodes.

9. In well logging apparatus, he combination of an electrode array adapted to be lowered into a bore hole, Said array C0Inprising inner and outer pairs of longit1di11ally Spaced-apart electtodes and an electrode inter- 1Tle(1iate the electrodes of said inner pair, an1plifier means having input terlnina1s connected t0 a Teference poil1t longitudinally spaced apart from Said electrodes and t0 one of said Pairs of electrodes, respectively, and having output ter!inals connected to a reference point substantially at ground potential and t0 said other pair of electrodes, respectively, Said amplier means being connected fol' degenerative feedback between the output and input terIninals there0f, a Source of periodically varying voltage connected in Series vvith Said amplier input tern1inals, and fneans for obtaining indications of periodicauy valying p0tential dierence betvveen Said intermediate electrode and Said one pair of electrodes 10. In vvell logging apparatus, the combination of an electrode array adapted to be lowered into a bore hole, Said array con]prising inner and outer pairs of longitudinany Spaced-apart electrodes and an electrode intermediate the electrodes of said inner pair, an1plier Ineans having input terminals connected to a reference point 10ngitudinally Spaced apart fron1 Said electrodes and to one of said pairs of electrodes, respectively, and having output ternlinals connected to a reference point Sub- Stalltially at ground potential and to Said other pair of electrodes, respectively, said a[npliner means being con- Ilected for degenerative feedback betvveen the output and input terminals thereof, a Source of periodically varying voltage connected in series with Said an1plilier inpllt ter Tlilals, and means connected in circuit With said amplier output terninals for obtaining indications of a periodically varying Signal in said anpliiiel' output.

ll. In well logging apparatus, the c0nbination of an electrode array adaped to be iowered into a bore hole,

Said array con1prising inner and outer pairs of longitudinally Spaced apart electrodes and an electrode intel Inediate the electrodes of Said inner pair irst alternating current Source Tneans having ter[ninals connected to a reference point 10ngitudinally Spaced apart from said electrodes and to one electrode in one of said airs, re- Spectively, Second alternating current Source means having terminals connected to a reference oint10ngitudinaly Spaced apart fron Said electrodes and the other elec trode of Said one Pair, respectively, means for Inaintaining the eectr()deS Of Said other pair at Substantiany the Same pOtental vvith respect to ground, and means fol 0btaining indications of the potential dieence between said intermediate electrode and at least one 0f he electrodes of said 0thel pair 12. II1 wen logging apparatus, the combination of a plurality of electrodes Inounted for n10venent through a bore hole in Spaced apart relation, adjustable means for passing electlic current betvveen one of said electrodes and a reference point 1011gitudina11y Spaced apart ther...` froIn, and means responsive to potential difference between another of Said electrodes and a reference point 10ngitudina1y spaced apart tl1erefrom for controlling said adju table neans to Inaintain said otential dierenCe at a Teference value' 13. In a fnethod of investigating an electrial property of earth fornlations traversed by a bore hole Containing a conducting li(1llid, tlle steps of disposing in a bore hole at least three 1()I1gitudilally spaced apart electrodes, n10ving Said elctrodes aS a unit to dierent positions in the bore hole, passing cu1Tent between a reference point longitudinauy Spaced apart from Said electrodes and two p0ints 10cated near the t'() outer electrodes, respectively, 0f Said three, adjusting the intensity of the current oWing at said points at each of Said I)()Siti()11s of the electrode aS required to Tnaintain Said two outer electrodes at a substantially constant p0tentia1 With respect to a Tefefence point Substantially at ground p0tential, and obtaining indications of a function of the intensity of the current fiowing at Said oints 14. A n1eth0d of Inaking an electric g of the fornations adjacent a well Which contains an electrically COn ductive medium, that comprises introducing a rSt elec trical current int0 a nrst portion of said electrically conductive nlediuln in a nlanner Such that said iirst electrical current vill have a Substantial vertical conponent, int0 ducing a Second electrical current of a polarity opposite to that of said iirst electrical current into a Second Portion vetically Spaced ffon1 said 1rSt poftion of Said electricany conductive Inedium in a manner Such that Said second electrical current vill have a Substantia1 vertical con1- ponent, Whereby the 0v of the vertical components of the current in opp0site directions in Said portions Vvill create a region between said portions of Substantially equal p0tential with respect to remote p0ftions of Sai i electrically conductive medium, detecting variations in said p0tential, enp10ying Said detected variations to n1aintain the region of equal potential between Said rSt and Second p0rtions of Said electrically conductive nlediuIn and obtaining indications of a function of the current conducted bevveen Said equal potential region and the f0rnlation adjacent theret0 S. A method of making an electric log of the formations adjacent a Well which contains an electrically Conductive Inediun1, that c0nprises introducing a HSt alter nating electrical current into a rSt portion of Said electrically conductive nedium in a manner Such that Said nrst aternating electrical current vvill have a Substantial vertical c0mponent, introducing a second alternating electrical current of an instantaneous p0larity 0pposite t0 that of Said rSt electrical cuffent int0 a second portion verticaly Spaced from said first portion 0f Said electrical ly conductive medium in a n1anner Such that Said Second aternating elecrical current will have a Substantial vertical` con1ponent, Whereby the instantaneous OW 0f the vertical components of the alternating current in 0pp0site directions in Said portions vill create a regi011 betvveen Said Portions of Substanially equal p0tential With respect to rern0te portions of Said electrically conductive nedium, detecting variations in Said p0tentia, enTploying Said detected variations t0 nlaintain the region of equal p0tential between Said iirst and second portions of Said electrically conductive mediunl and obtaining indications of a func tion of the alternating current conducted betvveen said equal p0tential region and the forn1ation adjacent theret0.

16' A method of making an electric log of the formations adjacent a well Which contains an electrically conductive nediun, that conprises introducing a fil St electrical current into a TSt portion of Said electfically conductive n1ediuIn in a Inanner Such that Said first electrical current Will have a Substantial vertical component, intr0 ducing a Second electrical current of a polarity opposite 0 that of Said Hrst electrical current into a Second Portion vertically spaced fron1 Said Hrst portion of said electrically conductive medium in a nlanner such that Said second electrical current vvill have a Substantial vertical con1 onent, Whereby the oW of the vertical c0nponents of the current in opposite directions in Said portions Wil! create a region between Said portions of Substantially equal potential vvith respect to reIn()te portions of said electrically conductive medium, detecting Variations in Said p0tentia, emp10ying the detected variations to vary the electrical current inroduced int0 one of said 0rtions of the conductive medium t() reestablish Said region 0f equal p0entia, and obtaining indications of potential dieTence betvveen 10ngitudinally spaced apart poij1ts in Said region.

lefee|ceS (:ied in the le of this patent UNITED STATES PATENTS 2,084,143 Hummel Ju11e l, 1937 Z,347,794 Piety May Z, 1944 z,446,303 0Wen Aug. 3, 1948 z,92,l2 Don Apr. 8 19SZ 

